A differential-stroke internal combustion engine is disclosed in U.S. Pat. No. 5,243,938, which is incorporated herein by reference in its entirety. In the differential-stroke engine, the piston completes four separate strokes—intake, compression, power, and exhaust—during one crankshaft revolution. An inner piston portion slides along a respective cylinder bore wall as guided at a chamber end by the piston crown. The inner piston portion is coupled to a piston stem sliding along a piston pin penetration, which makes a lengthwise linear motion along the cylinder axis as a piston lever swings to make the strokes of the inner piston portion. This induces undesirable stresses on the components and may cause premature wear and tear, for example on the piston ring lands, on the piston stem and on the cylinder wall. What is needed then is a differential-stroke internal combustion engine that combines the advantages of four strokes of the piston with the advantages of one revolution of the crankshaft per cycle without inducing premature wear and tear and undesirable stresses on piston train components.
In one aspect, embodiments disclosed herein relate to a differential stroke reciprocating internal combustion engine having an engine shaft and a piston configured to reciprocate within a cylinder chamber comprising an inner piston part, a piston stem coupled at a first end to said inner piston part, an outer piston part which serves as a carrier for said inner piston part and is connected to said engine shaft, wherein said inner piston part is configured to operate on a cycle different from that of said outer piston part, and a control and linkage assembly coupled to said engine at an anchor point, and said control and linkage assembly pivotally coupled at a second end of said piston stem defining a copy point, wherein said control and linkage assembly guides and defines the movement of said copy point to be substantially aligned with an axis of said cylinder chamber.
In other aspects, embodiments disclosed herein relate to a control and guide apparatus for use with a piston having a piston stem disposed within a cylinder of an internal combustion engine, said control and guide apparatus defining a four-bar-linkage comprising a piston lever-link-bar, a fulcrum-link bar, a force-link bar, and a rocker-link-bar, wherein said four-bar-linkage is defined and located by a first hinge junction of a first end of said fulcrum-link bar and a first end of said rocker-link bar, a second hinge junction of a second end of said fulcrum-link bar and said piston lever-link-bar, a third hinge junction of a second end of said rocker-link bar and a first end of said force-link bar, and a fourth hinge junction of a second end of said force-link bar and said piston lever-link-bar, wherein said piston lever-link-bar is pivotally coupled at one end to said piston stem to define a linear lengthwise motion for said piston stem along said cylinder axis.
In yet other aspects, embodiments disclosed herein relate to a method of using a piston-train control and guide apparatus for an internal combustion engine including an inner piston part having a piston stem and moving within a cylinder under the guidance of said piston stem, the method comprising providing a piston-train control and guide apparatus comprising a piston lever-link-bar hingedly coupled at a first location to an end of said piston stem defining a copy point and a linkage assembly coupled to said piston lever at a second location of said piston lever, and said linkage assembly further hingedly coupled to said engine at a location defining an anchor point, and actuating said linkage assembly and moving said copy point in a linear parallel motion within said cylinder substantially along a cylinder axis.